Electrostatic discharge is a concern in the design, manufacture and handling of integrated circuits (ICs). Electrostatic discharge events occur when a charged element moves into proximity of or directly contacts the terminals of an IC. Static discharge events can have potentials of many thousands of volts. ESD events can occur when the integrated circuit is not powered, during assembly and test, as well as when the integrated circuit is in use. Static can accumulate on tools, probes, machines, or even human bodies that can discharge into an integrated circuit. If no circuit protection is provided, the static discharge can cause destructive damage to the transistors or circuitry formed inside the integrated circuit. ESD protection is particularly important when the integrated circuit device is unpowered. If the ESD protection circuitry is still active when the device is powered, the ESD circuit design needs to be arranged to avoid inadvertently triggering during normal device operation.
The local interconnect network (LIN) standard refers to a serial network formed by an industry group, the LIN consortium, in the 1990s. LIN was designed as an inexpensive alternative interface to a prior approach, the controller area network (CAN) bus used in automobile connections. A LIN interface allows inexpensive components to network within an automobile. LIN uses a low cost single wire, non-shielded network that connects all the LIN components on a sub-net. The core of the LIN hardware is a single-wire transceiver that uses two complementary logic levels with a maximum data rate of twenty kilobits per second (kbps). The dominant value, Logic 0, is considered a voltage level that is 40% or less of the power supply level. The opposite value, Logic 1, is a recessive value and is considered a voltage of 60% of the power supply voltage of higher. The LIN bus is pulled high by resistors and can be driven low. The power supply is commonly 15V but may be in a range of 7V to 18V. The bus master typically has a 1K ohm pull-up resistor coupled through a diode to the battery supply voltage. Slaves typically have a 30K ohm pull-up resistor coupled through a diode to the battery voltage. LIN transceivers on the shared LIN bus operate in a wired-AND configuration where any permitted transceiver may pull the bus toward ground during operation, to indicate a Logic 0. All transceivers must be inactive to allow the pull-up resistors to return the bus to Logic 1. The use of the single wire, non-shielded network LIN connection may result in severe ESD, electromagnetic interference (EMI) and noise components that are input into any LIN transceiver while it is being plugged into, removed from, or operated on the LIN bus. For reverse polarity insertion protection and general robustness, the LIN interface specifies that a LIN transceiver is to withstand voltages from −24V to 60V, which is considered a high voltage range for integrated circuits.
In high voltage applications such as the circuitry for a LIN transceiver, back-to-back silicon controller rectifiers (SCRs) are commonly used to provide bidirectional ESD protection.
A common noise immunity test used for testing a LIN transceiver is the direct power injection (DPI) test. In this test, a high frequency, high power sinusoidal signal is applied to a transceiver circuit input or output terminal and the response of the transceiver is monitored. This test can trigger ESD circuitry.